Passive acoustic power spectra to monitor and control processing

• US 4,973,386 A
• Filed: 06/29/1988
• Issued: 11/27/1990
• Est. Priority Date: 07/13/1987
• Status: Expired due to Term

• Current Assignee: Exxon Research and Engineering Company (Exxon Mobil Corporation)
• Original Assignee: Exxon Research and Engineering Company (Exxon Mobil Corporation)
• Inventors: Cohen, Roger W., Callegari, Andrew J., Cody, George D., Elzinga, Eugene R. Jr.
• Primary Examiner(s): Woodard, Joye L.
• Application Number:
  US07/212,762
• Time in Patent Office: 881 Days
• Field of Search: 201/1, 201/23, 201/31, 201/41, 201/37, 202/270, 208/DIG. 1, 208/48 R, 208/127, 208/157, 208/163, 422/139, 422/140, 73/579, 73/590, 73/659
• US Class Current: 201/1
• CPC Class Codes: C10B 55/10 according to the "fluidised bed" technique
• CPC Class Codes: G01B 17/02 for measuring thickness
• CPC Class Codes: G01N 2291/02827 Elastic parameters, strength or force
• CPC Class Codes: G01N 2291/02854 Length, thickness
• CPC Class Codes: G01N 29/046 using the echo of particles imparting on a surface; using acoustic emission of particles investigating concentration of particle suspensions G01N15/06; devices for measuring flow of solids in suspension G01F1/74
• CPC Class Codes: Y10S 208/01 Automatic control

Abstract

A process for the detection and measurement of wall coke at a specific location in a fluid bed coker through the measurement of the vibrations of the external shell of the coker at the location.

Claims

1. A process for the non-intrusive passive acoustic detection and measurement of a change in thickness of a wall defining a reactor for processing material, wherein said change in thickness is due to erosion of said wall or material buildup on said wall using wall vibrations produced by a source within said reactor comprising:

(a) measuring the wall vibration of said reactor wall and then determining a first power spectrum indicative of the measured wall vibrations as a function of frequency at a time t=0;

(b) operating said reactor for a time, t;

(c) measuring the wall vibrations of said reactor wall and then determining a second power spectrum indicative of the measured wall vibrations as a function of frequency at said time, t;

(d) determining a frequency shift of a resonance on said first spectrum from the corresponding resonance on said second spectrum, and;

(e) correlating said frequency shift with the change in thickness of the reactor wall.

2. The process of claim 1 wherein said reactor is a fluid bed coker reactor and said change in thickness of said wall is due to coke buildup on the interior surface of said wall.

3. The process of claim 1 wherein said steps of measuring said wall vibrations are performed by using an accelerometer attached to the exterior surface of said reactor wall.

4. The process of claim 1 wherein said step of correlating said frequency shift with the change in thickness of said wall, D_i (t), is performed using ##EQU2## where f_i (t) is the frequency of said resonance at said time, t, f_i (o) is the frequency of said resonance at said time, t=0, and C is the effective compressional sound velocity of said reactor wall.

5. The process of claim 1 further comprising the step of displaying said change in thickness of said wall.

6. The process of claim 1 wherein said source for producing said wall vibrations is an open flame within said reactor.